This appears to be just another bug though. The maintenance panel which shows when a vet or keeper last visited isn't being updated. It is the actual variable that is not being updated not just the UI.
I just got the message for a habitat, that keeper hadn't been there in a long time. I checked. There was a keeper, in the habitat at that exact moment, and the UI said 1 year.
I called a keeper, after the keeper that was in there left, and he turned around and went back to the habitat, and the variable updated.